Shooting someone who was not threatening them.
And yes, I know they claim that their lives were in danger.
Of course, if their lives were in danger and the shooting was eminently justified one must ask: why tamper with evidence at the scene? Why fail to fire a full report?
That's the question the court had to consider.
A fleeing drug smuggler is certainly a danger to them when they claim they saw him turn around with something in his hand. Even if it was later found to be a rock, rocks can kill.
Add to that the prosecutor suppressing evidence at the trial and this whole thing looked much worse than it was.
If the jury had known that the perp was a drug smuggler and that the agents were at least part right they would not have gotten such long sentences.
Probably no jail time just some punishment for the reporting problems.